Carbon-coating small-molecule organic bipolar electrodes for symmetric Li-dual-ion batteries

A novel small organic molecule namely N,N'-bis(2-anthraquinone)-dihydrophenazine (DAQ-DPZ, 270 mAh/g) with n-p-n molecular heterojunction configuration is designed as the bipolar electrode material for Li-dual-ion batteries. To delay the dissolution for small-molecule organic electrodes, DAQ-DPZ is further coated by a protective carbon layer (DAQ-DPZ@C) through the process called surface self-carbonization. As expected, the resulting DAQ-DPZ@C can show the peak discharge capacity of 269 mAh/g and high median potential of 2.62 V in 1.6–4.4 V (vs. Li+/Li), corresponding to the peak energy density of 704 Wh kg−1 in Li-dual-ion half cells. Furthermore, DAQ-DPZ@C in the symmetric Li-dual-ion batteries can deliver the peak discharge capacity of 88 mAh/gcathode and the peak energy density of 113 Wh kg-1cathode, stably running for over 5000 cycles. To the best of our knowledge, these results are the top ones for small-molecule organic bipolar electrodes in the symmetric Li-dual-ion batteries.